Biofilm growth leads to short-circuit current losses of up to ~30% under accelerated conditions
Extracellular polymeric substances (EPS) bind dust into stable layers, making removal more difficult
Microbial pigments absorb light in the 400-500 nm range, overlapping with the silicon response
Solar deployment continues to expand rapidly across both utility-scale and distributed segments, with installations increasingly concentrated in high-irradiance regions. As deployment grows, maintaining performance while keeping operating costs low has become increasingly important.
Soiling is one of the persistent loss mechanisms in photovoltaic systems. It is typically associated with dust accumulation on module surfaces, especially in arid and high-irradiance regions. Over time, these deposits reduce light transmission and lower energy yield. Cleaning strategies and performance models are therefore largely based on the assumption that soiling is a physical process driven by particulate matter.
A recent study based on modules deployed in Chile’s Atacama Desert shows that this assumption is incomplete. The work combines field sampling with controlled laboratory analysis to examine the role of microorganisms in soiling. The results indicate that microbial activity actively contributes to surface deposits and associated performance losses, rather than acting as a passive presence.
Samples from operating systems revealed extremophilic bacterial communities on module glass. Genera such as Arthrobacter, Kocuria, and Dietzia were identified. These organisms tolerate high UV exposure, low humidity, and limited nutrients, enabling long-term survival on exposed PV surfaces.
The study shows that the biofilm develops rapidly. Initial microbial attachment evolves into structured layers embedded in extracellular polymeric substances. Within days, isolated cells form dense networks covering the surface. The EPS matrix binds mineral dust and organic matter, creating cohesive layers with higher mechanical stability.
This changes how soiling behaves. Deposits are no longer loose and easily removed. Dust becomes embedded in a biologically active matrix. In such a scenario, cleaning methods such as dry brushing or water rinsing show limited effectiveness. Even after cleaning, residual material remains, allowing faster re-accumulation.
The biological component also introduces an additional optical loss pathway. Certain strains, particularly Dietzia, produce carotenoid pigments, which absorb light in the 400-500 nm range. This overlaps with the spectral region where silicon solar cells generate a large share of current, reducing the amount of usable light reaching the cell. I-V analysis shows a reduction in short-circuit current as biomass increases. After about 7 days of biofilm growth, losses ranged from around 11% to over 30%, depending on surface coverage.
While these results are based on accelerated conditions, they align with field observations in desert installations. It was observed that microbial activity can amplify conventional dust-related losses by increasing adhesion, reducing transmittance, and limiting cleaning efficiency.
The findings suggest that soiling should be treated as a combined bio-physical process. For system design and O&M, this means that conventional cleaning approaches may be insufficient. Solutions such as biofilm-resistant coatings or cleaning methods that disrupt EPS structures could become relevant as PV deployment expands in arid regions.
The full paper, titled Microbial Contribution to Soiling and Its Impact on Photovoltaic Module Soiling in Arid Zones of the Atacama Desert, presents a detailed analysis of microbial biofilm formation and its impact on optical losses and PV performance.